The present invention relates to a method of and an arrangement for milling root butts of round timber, wherein a rotatable milling tool mounted on a milling shaft is brought into abutment against a trunk to be worked by an adjusting device, and then the root butt is milled out by relative rotary movement between the trunk and the milling tool to a desired trunk diameter.
Root butts interfere with working of round timber. This is true, for example, for transportation on elongated conveying devices in which the root trunks are hooked and block the transportation. This is also true for round timber storage in sorting boxes in which rumbling trunks are located in inclined position and often slide so that they engage with the trunks in the subsequent boxes, whereby the boxes emptying with stapler or crane became very difficult. Further disturbances involve plank impacts on railings, fixedly running circular saws, difficult cut guidance in the event of blocked band saws, etc. Straightening of the trunks involves considerable time and especially when a root butt has been clamped and must be released with great efforts by a hand saw and hand spike.
There are automatically operating root reducers which mill the root butts to the shaft diameter provided by the trunk. The known arrangements of this type operate in accordance with the following principle: The trunk to be worked is placed on a V-shaped block provided with driving roller chains. The trunk is loaded from above by a hold-down element which is also provided for supporting the rotation of the trunk with a driving roller chain or with a driving pressing wheel pressed against the outer surface of the trunk. During rotation of the trunk about its longitudinal axis, a milling tool is moved laterally from above parallel to the axis of the trunk and progressively mills the root butt. The milling tool can be mounted in a support which is hydraulically liftable and lowerable. Thereby the milling depth can be changed and adjusted as needed. The arrangement of the milling tool and the position of the supporting block guarantee that all trunks are reduced, regardless of their root diameter, parallel to the line of alignment of their outer surface.
All known arrangements are based on the principle of a relative movement between the trunk and the milling tool obtained by rotation of the trunk around its longitudinal axis, whereas the milling tool during the milling step is retained stationarily. The disadvantage of this principle is the construction expenses required particularly for the long trunks to drive them in rotation. The further disadvantage is that the milling tool which engages laterally from above the trunk during the milling process applies forces which try to press it upwardly. Thereby a non-even abutment of the trunk takes place, which reduces the service life of the milling tool. Finally, it is not possible with the fixedly held milling tools during milling to provide working corresponding to the heavily bent trunk ends deviating from the longitudinal axis of the trunk. This leads to a non-uniform milling process. The arrangements of the above general type are disclosed in prospectuses and partially in the German Offenlegungsschrift DE-OS 2,847,353.